Tuesday, April 7, 2009

At the Root of Things

When the weather suddenly changes from winter to summer as it has this week on the coast, it can be tempting to run directly to the garden center, do not pass go, and get those beautiful new plants into your garden.  Resist.  The success of your landscape plants and vegetable garden is directly tied to the effort you put into their very foundation, the soil.

For coastal residents who move from inland locations like the Willamette Valley or east of the Cascades, our soil on the coast can be a mystery.  One major factor here is rainfall.  In areas of high annual rainfall, like the Oregon coast, the pH tends toward the acid (low reading) side of the spectrum.  Acid soils like ours produce happy rhododendrons and other acid-loving plants, but don't necessarily make for lush green lawns.  If you are from the mountain states, you may be used to very alkaline soil (high pH) which is typical of arid regions.  You may never have to touch a bag of lime back home.  In our area however, depending on what you want to grow, it will be required for the health of your plantings.  Certainly a soil test will give you more concrete answers, but when in doubt you can guess that your soil on the Oregon coast will be acidic to neutral rather than alkaline, and yearly additions of lime will be helpful.

Soil texture and structure can vary hugely depending on where your house is located and in what coastal area. This is a dynamic place, shaped by both the ocean and our northwest volcanoes, with centuries of forest cover to boot.  You might be on the oceanfront with almost pure sand, closer to the basalt cliffs with very little topsoil layer over the rock, or lucky enough to have your home in an area that grew stately spruces and hemlocks for many years before housing replaced them.  If the builder didn't remove it all, areas like these can have deep, rich organic topsoil that holds moisture well and supports a wide range of plantings.  Do some investigation before you put a lot of money into new landscaping, and if necessary consult the local extension office or local nursery for advice and analysis of your soil type.

Aside from lime, the most frequently applied amendment for coastal soils is likely "compost."  This refers to organic materials that have gone through a decomposition process until the components turn into a dark, crumbly material similar in color and texture to loamy soil.  It should smell mild, not ammonia-like, and have a fairly consistent fine texture.  Small pieces of woody material is ok, but avoid compost with large woody chips as it might impede the plants' uptake of nitrogen.  This is not important if you are amending soil for woody plants, they will do just fine with chunky compost, but if you are planting a lawn, veggies or annual flowers, it's best to stick with a finer material.  Compost works wonders: it improves texture, helps retain moisture in sandy soil and improve drainage in heavy soil, creates more pore-spaces for air and water around roots, and provides some protection against temperature extremes when applied as a mulch.  If you spread and work in the compost a week or so early, your soil will be ready at planting time.

When growing plants with high nutritional needs like vegetables, fruits or showy annuals, it's a wise course to first amend those beds with a product like bagged steer or chicken manure.  In addition to improving the soil texture with added organic matter, the composted animal manures will provide some nitrogen and other essential minerals to the plants throughout the season.  It should not be solely relied upon for fertilization with heavy-feeding plants, but will give a good "baseline" of food to get things growing quickly and reduce fertilizer needs.  It's important to select composted manure, hopefully screened to a fine texture, as fresh manures can potentially burn the plants or rob nutrients while this material is trying to break down.

Lastly, remember that mulches after planting can help your soils to retain valuable moisture during the dry season and protect the soil from the pounding rains of winter.  Mulches of hemlock or Douglas-fir bark are common on the central coast, and will improve not only the appearance of your landscape beds but the performance of what lies beneath.  Plan on applying 2" of mulch at least every other year, preferably in spring after winter storms have passed.


  1. Do you know of any good sources for quality soil for some new raised beds (veggies) in the Lincoln City area? Love the blog!

  2. Hi Jason,
    As you know we are limited... I usually get the "base" mix from Devils Lake Rock, it helps if they just mixed up a new batch instead of old stuff that sat out in the rain all winter. Pretty fresh this week. Because it tends to be very sandy, I usually then add a good amount of finished compost (could be veggie/worm bin/steer or chicken manure) and lime. Usually this is sufficient for your first season, then you will want to continually improve the soil with cover cropping fall-spring and more compost. Test the pH as you go, so you can adjust as needed.